You may have better luck contacting Apple rather than random strangers on the internet.
This.
Where are you seeing the charge? Could be the credit card has been compromised by some other source. Not sure if possible today, but back in the day, credit card scammers would make purchases on iTunes to test the cc number is still viable before using it on something more valuable.
Do as Banglazed said. If not seeing a purchase there, could be your CC information has been stolen recently (eg. the recent Saks/Lord & Taylor, Delta Airlines, Sears breaches).